Parsing string containing doubles

[Daniel Lidström]

Hi,

I'm currently using this method to extract doubles from a string:

System::String* sp = S" ";
System::String* tokens[] = s->Trim()->Split(sp->ToCharArray()) ;
m_Northing = System::Double: :Parse(tokens[0], nfi);
m_Easting = System::Double: :Parse(tokens[1], nfi);
m_Elevation = System::Double: :Parse(tokens[2], nfi);

However, only strings that contain one " " are correctly parsed. How can I
do this for strings that contain arbitrary number of " " between doubles?
I.e.:
"79812.862 15532.942 1565.570" is ok, while
"79812.862 15532.942 1565.570" is not ok.

With C++ I would just use a stringstream. Can I do this with MC++ too? I
have not yet figure out how.

Thanks!

--
Daniel

[Niki Estner]

Re: Parsing string containing doubles

There is no real equivalent to C++'s scanf or iostreams in .NET. The thing
that comes closest to these are regular expressions (C# syntax):

using System.Text.Reg ularExpressions ;
....
Match m = Regex.Match(you rString,
@"^\s*([0-9.,]+)\s+([0-9.,]+)\s+([0-9.,]+)\s*$");
if (m.Success)
{
Console.WriteLi ne(System.Doubl e.Parse(m.Group s[1].ToString()));
Console.WriteLi ne(System.Doubl e.Parse(m.Group s[2].ToString()));
Console.WriteLi ne(System.Doubl e.Parse(m.Group s[3].ToString()));
}

However, Regex's are far more powerful, and it may take some time to get
used to them. It's worth the effort though, IMO.

Niki

"Daniel Lidström" <someone@micros oft.com> wrote in
news:t2mlxmzd75 5v$.1rdd7b0xfxd c2.dlg@40tude.n et...[color=blue]
> Hi,
>
> I'm currently using this method to extract doubles from a string:
>
> System::String* sp = S" ";
> System::String* tokens[] = s->Trim()->Split(sp->ToCharArray()) ;
> m_Northing = System::Double: :Parse(tokens[0], nfi);
> m_Easting = System::Double: :Parse(tokens[1], nfi);
> m_Elevation = System::Double: :Parse(tokens[2], nfi);
>
> However, only strings that contain one " " are correctly parsed. How can I
> do this for strings that contain arbitrary number of " " between doubles?
> I.e.:
> "79812.862 15532.942 1565.570" is ok, while
> "79812.862 15532.942 1565.570" is not ok.
>
> With C++ I would just use a stringstream. Can I do this with MC++ too? I
> have not yet figure out how.
>
> Thanks!
>
> --
> Daniel[/color]

[WizyDig]

Re: Parsing string containing doubles

Have you considered using replace to clean your string before you call
split? You could replace the " " with " ". Just a thought then you
would have to change your other code. It only requires one extra line
per type of clean up you need to do.

Wiz

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[Niki Estner]

Re: Parsing string containing doubles

What if the input is separated by 3 spaces?
....or 4?

Niki

"WizyDig" <someone@micros oft.com> wrote in
news:uI%230vnTh EHA.3148@TK2MSF TNGP10.phx.gbl. ..[color=blue]
> Have you considered using replace to clean your string before you call
> split? You could replace the " " with " ". Just a thought then you
> would have to change your other code. It only requires one extra line
> per type of clean up you need to do.
>
> Wiz
>
> *** Sent via Developersdex http://www.developersdex.com ***
> Don't just participate in USENET...get rewarded for it![/color]

[Daniel Lidström]

Re: Parsing string containing doubles

On Wed, 18 Aug 2004 15:44:26 +0200, Niki Estner wrote:
[color=blue]
> There is no real equivalent to C++'s scanf or iostreams in .NET. The thing
> that comes closest to these are regular expressions (C# syntax):
>
> using System.Text.Reg ularExpressions ;
> ...
> Match m = Regex.Match(you rString,
> @"^\s*([0-9.,]+)\s+([0-9.,]+)\s+([0-9.,]+)\s*$");
> if (m.Success)
> {
> Console.WriteLi ne(System.Doubl e.Parse(m.Group s[1].ToString()));
> Console.WriteLi ne(System.Doubl e.Parse(m.Group s[2].ToString()));
> Console.WriteLi ne(System.Doubl e.Parse(m.Group s[3].ToString()));
> }
>
> However, Regex's are far more powerful, and it may take some time to get
> used to them. It's worth the effort though, IMO.[/color]

How would I write this in MC++? I tried this but got compilation errors:

#using <System.dll>

using namespace System::Text::R egularExpressio ns;
....
Match* m = Regex::Match(s,
"^\\s*([0-9.,]+)\\s+([0-9.,]+)\\s+([0-9.,]+)\\s*$");
if( m->Success ){
m_Northing = System::Double: :Parse(m->Groups->Item(1)->ToString());
m_Easting = System::Double: :Parse(m->Groups->Item(2)->ToString());
m_Elevation = System::Double: :Parse(m->Groups->Item(3)->ToString());
}

(113) : error C2064: term does not evaluate to a function taking 1
arguments
(113) : error C2227: left of '->ToString' must point to class/struct/union

113 refers to m_Northing = ... line. Also, is the regular expression
written to be equivalent with the CS example? What does the @ at the start
of the CS RE mean?
Thanks!

--
Daniel
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[Niki Estner]

Re: Parsing string containing doubles

"Daniel Lidström" <someone@micros oft.com> wrote in
news:senj9alb6n g$.18b5cc33b2t9 3.dlg@40tude.ne t...[color=blue]
> ...
> How would I write this in MC++? I tried this but got compilation errors:
> ...[/color]

Item is an indexer; Try:
m_Northing = System::Double: :Parse(m->Groups->Item[1]->ToString());
m_Easting = System::Double: :Parse(m->Groups->Item[2]->ToString());
m_Elevation = System::Double: :Parse(m->Groups->Item[3]->ToString());
[color=blue]
> Also, is the regular expression
> written to be equivalent with the CS example?[/color]

Yes, I think so.
[color=blue]
> What does the @ at the start of the CS RE mean?[/color]

In a "normal" C# string you have to escape backslashes like in C. However if
you prefix the string literal with @, you can put in backslashes like any
other character. Nice feature for paths or regular expressions.
Maybe you should have a look at a tool like Expresso
(http://www12.brinkster.com/ultrapico/Expresso.htm). It's perfect for
testing a regular expression on sample data, and it can create correct MC++
code (with correctly escaped backslashes).

Just curious: why do you use MC++? I tend to use C# where I can, because I
don't like all those special keywords like "__gc", "__value" and so on.

Niki

[Daniel Lidström]

Re: Parsing string containing doubles

On Thu, 19 Aug 2004 12:21:41 +0200, Niki Estner wrote:
[color=blue]
> Maybe you should have a look at a tool like Expresso
> (http://www12.brinkster.com/ultrapico/Expresso.htm). It's perfect for
> testing a regular expression on sample data, and it can create correct MC++
> code (with correctly escaped backslashes).[/color]

That's a great tool! Many thanks for pointing me to it.

--
Daniel

[WizyDig]

Re: Parsing string containing doubles

This small chunk of code will do what you are looking for Niki.


string t = " some string with odd number of spaces";
int i = t.IndexOf(" ",0);
int j = t.IndexOf(" ",0);
while( i > 0 || j > 0)
{
t = t.Replace(" "," ");
i = t.IndexOf(" ",0);
j = t.IndexOf(" ",0);
}

Hope that helps

-Wiz

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